1. Field of the Invention
The present invention relates to a recording element substrate having a plurality of recording elements, and a recording head having the recording element substrate.
2. Description of the Related Art
For printing at a higher speed using a recording head, simultaneous driving of as many heaters (recording elements) as possible are desirable. Such driving, however, increases a current flowing through line (wiring). This may preclude the generation of desired thermal energy at the heaters due to voltage drop caused by parasitic resistance of the line (wiring). The variation in thermal energy leads to variable volumes of discharged ink, resulting in the problem of degraded image quality. To solve the problem, Japanese Patent Application Laid-Open No. 2001-277516 discusses a device in which a recording element substrate having a control circuit 1801 and a selection circuit 1802 controls the voltage across a heater R1 to be equal to that of a constant voltage generator Vr1. This circuit configuration maintains the thermal energy at the heater to be constant regardless of any voltage fluctuation, and stabilizes the volume of discharged ink droplets.
In the device discussed in Japanese Patent Application Laid-Open No. 2001-277516, the voltage fluctuation in one of a high-potential or low-potential power wiring is controlled to apply a constant voltage to a heater. The other power wiring for the heater is, however, only designed to have a wiring resistance that is suppressed enough for negligible voltage fluctuation.
Power lines (wirings) used on a substrate are getting narrower and longer and, thus, have an increased resistance than that of a conventional wire. This increases the voltage fluctuation in the power wiring to a non-negligible level.